Temperature-Dependent Separation of CO2 from Light Hydrocarbons in a Porous Self-Assembly of Vertexes Sharing Octahedra.

Design of flexible porous materials where the diffusion of guest molecules is regulated by the dynamics of contracted pore aperture is challenging. Here, a flexible porous self-assembly consisting of 1D channels with dynamic bottleneck gates is reported. The dynamic pendant naphthimidazolylmethyl moieties at the channel necks provide kinetic gate function, that enables unusual adsorption for light hydrocarbons. The adsorption for CO2 is mainly dominated by thermodynamics with the uptakes decreasing with increasing temperature, whereas the adsorptions for larger hydrocarbons are controlled by both thermodynamics and kinetics resulting in an uptake maximum at a temperature threshold. Such an unusual adsorption enables temperature-dependent separation of CO2 from the corresponding hydrocarbons.

Trapping an Ester Hydrate Intermediate in a π-Stacked Macrocycle with Multiple Hydrogen Bonds.

Ester hydrates, as the intermediates of the esterification between acid and alcohol, are very short-lived and challenging to be trapped. Therefore, the crystal structures of ester hydrates have rarely been characterized. Herein, we present that the mono-deprotonated ester hydrates [CH3OSO2(OH)2]-, serving as the template for the self-assembly of a π-stacked boat-shaped macrocycle (CH3OSO2(OH)2)0.67(CH3OSO3)1.33@{[ClLCoII]6}·Cl4·13CH3OH·9H2O (1) (L = tris(2-benzimidazolylmethyl) amine), can be trapped in the host by multiple NH···O hydrogen bonds. In the solution of CoCl2, L, and H2SO4 in MeOH, HSO4- reacts with MeOH, producing [CH3OSO3]- via the ester hydrate intermediate of [CH3OSO3(OH)2]-. Both the product and the intermediate serve as the template directing the self-assembly of the π-stacked macrocycle, in which the short-lived ester hydrate is firmly trapped and stabilized, as revealed by single-crystal analysis.

Metalation of a Hierarchical Self-Assembly Consisting of π-Stacked Cubes through Single-Crystal-to-Single-Crystal Transformation.

Single-crystal-to-single-crystal metalation of organic ligands represents a novel method to prepare metal-organic complexes, but remains challenging. Herein, a hierarchical self-assembly {(H12L8)·([N(C2H5)4]+)3·(ClO4-)15·(H2O)32} (1) (L = tris(2-benzimidazolylmethyl) amine) consisting of π-stacked cubes which are assembled from eight partially protonated L ligands is obtained. By soaking the crystals of compound 1 in the aqueous solution of Co(SCN)2, the ligands coordinate with Co2+ ions stoichiometrically and ClO4- exchange with SCN- via single-crystal-to-single-crystal transformation, leading to {([CoSCNL]+)8·([NC8H20]+)3·(SCN)11·(H2O)13} (2).

In Situ Charge Modification within Prussian Blue Analogue Nanocubes by Plasma for Oxygen Evolution Catalysis.

A targeted defect-induced strategy of metal sites in a porous framework is an efficient avenue to improve the performance of a catalyst. However, achieving such an activation without destroying the ordered framework is a major challenge. Herein, a dielectric barrier discharge plasma can etch the Fe(CN)6 group of the NiFe Prussian blue analogue framework in situ through reactive oxygen species generated in the air. Density functional theory calculations prove that the changed local electronic structure and coordination environment of Fe sites can significantly improve oxygen evolution reaction catalytic properties. The modified NiFe Prussian blue analogue is featured for only 316 mV at a high current density (100 mA cm-2), which is comparable to that of commercial alkaline catalysts. In a solar cell-driven alkaline electrolyzer, the overall electrolysis efficiency is up to 64% under real operation conditions. Over 80 h long-time continuous test under 100 mA cm-2 highlights superior durability. The density functional theory calculations confirm that the formation of OOH* is the rate-determining step over Fe sites, and Fe(CN)6 vacancy and extra oxygen atoms can introduce charge redistribution to the catalyst surface, which finally enhances the oxygen evolution reaction catalytic properties by reducing the overpotential by 0.10 V. Both experimental and theoretical results suggest that plasma treatment strategy is useful for modifying the skeletal material nondestructively at room temperature, which opens up a broad prospect in the field of catalyst production.

Ultrahigh thermoelectric performance of Janus α-STe2 and α-SeTe2 monolayers.

Janus α-STe2 and α-SeTe2 monolayers are investigated systematically using first-principles calculations combined with semiclassical Boltzmann transport theory. Janus α-STe2 and α-SeTe2 monolayers are indirect semiconductors with band gaps of 1.20 and 0.96 eV, respectively. It is found that they possess ultrahigh figure of merit (ZT) values of 3.9 and 4.4, respectively, at 500 K, much higher than that of the pristine α-Te monolayer (2.8). The higher ZT values originating from Janus structures reduce lattice thermal conductivities remarkably compared with the pristine α-Te monolayer. The much higher phonon anharmonicity in Janus monolayers leads to significantly lower lattice thermal conductivity. It is also found that electronic thermal conductivity can play an important role in thermoelectric efficiency of materials with quite low lattice thermal conductivity. This work suggests the potential applications of Janus α-STe2 and α-SeTe2 monolayers as thermoelectric materials and highlights that using a Janus structure is an effective way to enhance thermoelectric performance.

Achieving stable photoluminescence by double thiacalix[4]arene-capping: the lanthanide-oxo cluster core matters.

Luminescence stability is a critical consideration for applying phosphors in practical devices. In this work, we report two categories of double p-tert-butylthiacalix[4]arene (H4TC4A) capped clusters that exhibit characteristic lanthanide luminescence. Specifically, {[Ln4(µ4-OH)(TC4A)2(DMF)6(CH3OH)3(HCOO)Cl2]}·xCH3OH (Ln = Eu (1), Tb (2); x = 0-1) with square-planar [Ln4(µ4-OH)] cluster cores and {[Ln9(µ5-OH)2(µ3-OH)8(OCH3) (TC4A)2 (H2O)24Cl9]}·xDMF (Ln = Gd (3), Tb (4), Dy (5); x = 2-6) with hourglass-like [Ln9(µ5-OH)2(µ3-OH)8] cluster cores are synthesized and characterized. By comparing 2 and 4, we find that several critical luminescence properties (such as quantum efficiency and luminescence stabilities) depend directly on the cluster core structure. With the square-planar [Ln4(µ4-OH)] cluster cores, 2 demonstrates high quantum yield (∼65%) and excellent luminescence stability against moisture, high temperature, and UV-radiation. A white light-emitting diode (LED) with ultrahigh color quality is successfully fabricated by mixing 2 with commercial phosphors. These results imply that high quality phosphors might be achieved by exploiting the double thiacalix[4]arene-capping strategy, with an emphasis on the cluster core structure.

From a Metal-Organic Square to a Robust and Regenerable Supramolecular Self-assembly for Methane Purification.

Porous supramolecular assemblies constructed by noncovalent interactions are promising for adsorptive purification of methane because of their easy regeneration. However, the poor stability arising from the weak noncovalent interactions has obstructed their practical applications. Here, we report a robust and easily regenerated polyhedron-based cationic framework assembled from a metal-organic square. This material exhibits a very low affinity for CH4 and N2 , but captures other competing gases (e.g. C2 H6 , C3 H8 , and CO2 ) with a moderate affinity. These results underpin highly selective separation of a range of gas mixtures that are relevant to natural gas and industrial off-gas. Dynamic breakthrough studies demonstrate its practical separation for C2 H6 /CH4 , C3 H8 /CH4 , CO2 /N2 , and CO2 /CH4 . Particularly, the separation time is ≈11 min g-1 for the C2 H6 /CH4 (15/85 v/v) mixture and ≈49 min g-1 for the C3 H8 /CH4 (15/85 v/v) mixture (under a flow of 2.0 mL min-1 ), respectively, enabling its capability for CH4 purification from light alkanes.

Ultrastable Photoluminescence Enabled by 1D Rare-Earth Metal-Organic Frameworks Based on Double Thiacalix[4]arene-Capped Nodes.

Luminescent stability is a vital factor that dictates the application of lanthanide luminescent materials. Designing luminescent lanthanide cluster nodes that form an extended framework with predictable linking patterns may help enhance the structural stability of the lanthanide complexes and hence lead to improved luminescent stability. Herein, we report a series of one-dimensional (1D) rare-earth metal-organic framework compounds, {Ln4(µ4-OH)(TC4A)2(H2O)2(CH3O)(HCOO)2(HCOOH)}·xCH3OH (Ln = Sm (1), Eu (2), Tb (3), Dy (4); x = 1-5), based on double thiacalix[4]arene-capped Ln4(µ4-OH)(TC4A)2 nodes. The axially capped Ln4(µ4-OH)(TC4A)2 nodes are connected equatorially by formate bridges to form zigzag 1D-metal-organic framework (MOF) chains, which further assemble into a quasi-two-dimensional (2D) structure via hydrogen bonding. These unique features result in a stable structure and therefore superior luminescent stability. For example, the Tb-based 1D-MOF (3) exhibits intensive green photoluminescence with a quantum yield of 53% and an average decay time of 1.33 × 106 ns. It maintains its integrated emission intensity at 96.5, 94.5, and 89.4% of the original value after being exposed to moisture (soaking in water for 10 days), elevated temperature (150 °C), and UV (15 days of continuous radiation), respectively, demonstrating excellent luminescent stability. We adopt the Tb-based 1D-MOF (3) as the green phosphor and successfully fabricate a prototype white-light-emitting diode (LED) with stable emission under long-term operation. Our synthetic strategy allows control over the linking pattern of lanthanide nodes, providing a predictive route to obtain lanthanide MOFs with improved luminescent stability.

Constructing π-Stacked Supramolecular Cage Based Hierarchical Self-Assemblies via π···π Stacking and Hydrogen Bonding.

Constructing supramolecular cages with multiple subunits via weak intermolecular interactions is a long-standing challenge in chemistry. So far, π-stacked supramolecular cages still remain unexplored. Here, we report a series of π-stacked cage based hierarchical self-assemblies. The π-stacked cage (π-MX-cage) is assembled from 16 [MXL]+ ions (M = Mn2+, Co2+; X = Br-, SCN-, Cl-; and L = tris(2-benzimidazolylmethyl)amine) via 18 intermolecular π-stacking interactions. The tetrahedral cage, consisting of four [MXL]+ ions as the vertexes and six pairs of [MXL]+ ions as the edges, features 48 exterior N-H hydrogen bond donors for hydrogen bond formation with guest molecules. By variation of the M2+/X- pair, the π-MX-cage demonstrates unique versatility for incorporating a wide variety of species via different hydrogen-bonding modes during the assembly of hierarchical superstructures. In specific, the π-MnBr-cages encapsulate acetonitrile (CH3CN) or cis-1,3,5-cyclohexanetricarbonitrile (cis-HTN) molecules in the central voids, while a core-shell tetrahedral inorganic cluster [Mn(H2O)6]@([Mn(H2O)4]4[Br42-]6) (Mn@Mn4-cage) is captured within the interstitial regions between cages. The π-CoSCN-cages are capable of stabilizing reactive sulfur-containing species, such as S2O42-, S2O62-, and HSO3- ions, in the hierarchical superstructure. Finally, H2PO4- ions are incorporated between π-CoCl-cages, resulting in an inorganic mesoporous framework. These results provide insights into further exploring the chemistry and hierarchical assembly of supramolecular cages based on π-π stacking intermolecular interactions.

[Recent developments in enhancing the efficiency of CRISPR/Cas9- mediated knock-in in animals].

Gene-editing technology can artificially modify genetic material of targeted loci by precise insertion, deletion, or replacement in the genomic DNA. In recent years, with the developments of zinc-finger endonuclease (ZFN), transcription activator-like effector nuclease (TALEN), clustered regularly interspaced short palindromic repeats/CRISPR- associated protein 9 (CRISPR/Cas9) technologies, such precise modifications of the animal genomes have become possible. Although gene-editing tools, such as CRISPR/Cas9, can efficiently generate double-strand breaks (DSBs) in mammalian cells, the homology-directed repair (HDR) mediated knock-in (KI) efficiency is extremely low. In this review, we briefly describe the current development of gene-editing tools and summarize the recent strategies to enhance the CRISPR/Cas9- mediated KI efficiency, which will provide a reference for the generation of human disease models, research on gene therapy and livestock genetic improvement.

Comparative investigation of the thermal transport properties of Janus SnSSe and SnS2 monolayers.

Recently, Janus two-dimensional (2D) materials as a new member of 2D derivatives have been receiving much attention due to their novel properties. In this work, the lattice thermal conductivity κL of the Janus SnSSe monolayer is investigated based on first-principles calculations, while that of the SnS2 monolayer is studied for comparison. It is found the the κL values of SnSSe and SnS2 are 13.3 and 11.0 W m-1 K-1 at room temperature, and acoustic branches dominate their thermal transport. Weaker phonon anharmonicity in SnSSe leads to a slightly higher κL, though it has weaker phonon harmonicity. The smaller Grüneisen parameters of TA and LA phonons lower than 1 THz in SnSSe indicate weaker phonon anharmonicity, resulting in a higher κL. Finally, the size effect and boundary effect are also investigated, exhibiting that the κL can further decrease at the nanoscale. Our work suggests that Janus SnSSe and SnS2 have a much lower κL compared with conventional transition metal dichalcogenides (TMDs) and are potential competitors in the thermoelectric field.

Prussian blue analogue-derived Ni and Co bimetallic oxide nanoplate arrays block-built from porous and hollow nanocubes for the efficient oxygen evolution reaction.

Effective oxygen evolution reaction (OER) catalysts composed of Earth-abundant transition metals are crucial for sustainable energy conversion and storage. Metal-organic frameworks (MOFs) with tunable compositions are promising precursors for the fabrication of hollow and porous electrocatalysts. However, pulverous MOFs usually suffer from agglomeration during pyrolysis, greatly reducing the activity of their derived catalysts. In this work, Prussian blue analogue (PBA) arrays with hierarchical multidimensional architecture were directly grown on nickel foam (NF) using a template-oriented method. The subsequent calcination in air allowed for obtaining NixCo3-xO4 nanoplate arrays consisting of porous and hollow nanocubes. The derived bimetallic NixCo3-xO4/NF required only an overpotential of 287 mV to achieve a current density of 10 mA cm-2 in 1.0 M KOH solution, which is much lower than that of the monometallic NiO and the RuO2 benchmark. The 3D intersectional architecture of the NixCo3-xO4 nanoplates and the porous and hollow nanocube subunits contributed to the large specific surface area and reduced charge-transfer resistance of the NixCo3-xO4/NF electrode. Density functional theory (DFT) calculations and post-OER characterization revealed that the incorporated Co was the active sites and electrochemical active CoOOH intermediates were in situ formed during the OER. Our study provides a facile and efficient strategy for the rational design of MOF-derived materials towards effective and low-cost electrocatalysis.

[MEK inhibitor PD0325901 significantly boosts ssODN-mediated HDR efficiency in porcine fetal fibroblasts].

There are two major pathways, homology-directed repair (HDR) and nonhomologous end joining (NHEJ), involved in double-strand break (DSB) repair. Single-stranded oligodeoxyribonucleotide (ssODN)-mediated homologous recombination repair is commonly used for animal site-directed genome editing, with great scientific and practical value. To improve ssODN-mediated HDR efficiency in the pig genome, we investigated the effect and molecular mechanism of mitogen-activated extracellular signal-regulated kinase (MEK) inhibitor PD0325901 on the HDR efficiency in porcine fetal fibroblasts (PFFs). The results showed that PD0325901 obviously increased the percentage of G2 and S phase cell populations and reduced the cell population ratio in the G1 phase of PFFs, and promoted the expression of HDR repair factor. At the optimal concentration of 250 nmol/L, PD0325901 increased the repair efficiency of ssODN-mediated GFP reporter vector by 58.8% and the directed editing efficiency of PFF DMD and ROSA26 locus by 48.16% and 17.64%, respectively. The results show that MEK inhibitor PD0325901 significantly promotes the efficiency of ssODN-mediated homologous-directed repair in the porcine genome, thus offering a new idea to generate genetically modified pigs more effectively.

[Effects of RNA interference on the porcine NHEJ pathway repair factors on HR efficiency].

Non-homologous end-joining (NHEJ) is the predominant DNA double-strand break (DSB) repair pathway in mammalian cells. It inhibits the efficiency of homologous recombination (HR) by competing for DSB targets. To improve the efficiency of HR in porcine fetal fibroblasts (PFFs), several RNA interference (RNAi) systems were designed to knockdown NHEJ key molecules, such as polynucleotide kinase/phosphatase (PNKP), DNA ligase IV (LIG4) and NHEJ1. The results show that siRNA significantly knocked down LIG4, PNKP and NHEJ1 expression. Suppression of PNKP dramatically increased the efficiency of single-strand annealing (SSA), double-strand DNA (dsDNA) and single-strand DNA (ssODN) mediated homology-directed repair (HDR) by 55.7%, 37.4% and 73.1% after transfected with the SSA-GFP reporter, HDR-GFP system or ssODN-GFP system, respectively; whereas knockdown of LIG4 and NHEJ1 repair factors significantly increased dsDNA or ssODN-mediated HDR efficiency by 37.5% and 76.9%, respectively.

[Progress and application of genome-edited pigs in biomedical research].

Genome editing technologies (GETs) can precisely alter the genomic sequences and modify the genetic information at the target site of an organism. Since the beginning of the 21st century, the GETs, including zinc finger nucleases (ZFN), transcription-activating-like receptor factor (TALEN), and clustered regularly interspaced short palindromic repeats/Cas endonucleases (CRISPR/Cas), have been successively developed. The GETs can easily engineer the targeted genomic site of animals to exhibit a desired phenotype(s), thereby providing valuable tools in biomedical research. The pigs are closely related to human, in terms of similarities in physiological properties and pathogenic characters. Thus, pigs have been used as important animal models in studies of human disease, xenotransplantation, and humanized organs regeneration. In this review, we summarize the development of the three GETs, research progress of genome-edited pigs as disease models and organ donors for xenotransplantation, and the prospects of their applications in future biomedical research.

Effects of parameters, plasmid dosages and topological structures on transfection efficiency of porcine fetal fibroblasts using different electroporators.

To obtain an ideal transfection efficiency of porcine fetal fibroblasts, fluorescence activated cell sorting (FACS) was used to optimize parameters for transfection of porcine fetal fibroblasts (PFFs) with ECM? 830, NEPA 21 and Nucleofector? 2b in different conditions such as electroporation parameters, plasmid dosages and topological structures. The results show that the optimum poring pulse parameter of NEPA 21 is voltage 200 V, continuous 3 ms, interval 50 ms, 3 times, voltage attenuation range of 10%; and the transfection efficiency of Nucleofector? 2b is highest under U-023 program. Under the optimum conditions, FACS analysis demonstrates that Nucleofector? 2b and ECM? 830 have the highest transfection efficiency when transfecting 10 µg supercoiled plasmids into PFFs, and 8 µg for NEPA 21. Supercoiled plasmids show higher transfection efficiencies than linearized plasmids. Moreover, Nucleofector? 2b has the highest transfection efficiency among the three electroporation instruments. This study paves the way to generate transgenic or gene editing pigs with high efficiency.

Understanding activity trends in electrochemical water oxidation to form hydrogen peroxide.

Electrochemical production of hydrogen peroxide (H2O2) from water oxidation could provide a very attractive route to locally produce a chemically valuable product from an abundant resource. Herein using density functional theory calculations, we predict trends in activity for water oxidation towards H2O2 evolution on four different metal oxides, i.e., WO3, SnO2, TiO2 and BiVO4. The density functional theory predicted trend for H2O2 evolution is further confirmed by our experimental measurements. Moreover, we identify that BiVO4 has the best H2O2 generation amount of those oxides and can achieve a Faraday efficiency of about 98% for H2O2 production.Producing hydrogen peroxide via electrochemical oxidation of water is an attractive route to this valuable product. Here the authors theoretically and experimentally investigate hydrogen peroxide production activity trends for a range of metal oxides and identify the optimal bias ranges for high Faraday efficiencies.

A compressed octa-hedral cobalt(II) complex in the crystal structure of di-aqua-[6,6'-sulfanediylbis(2,2'-bi-pyridine)]cobalt(II) dinitrate.

The asymmetric unit of the title salt, [Co(C20H14N4S)(H2O)2](NO3)2, comprises a [Co(C20H14N4S)(H2O)2]2+ cation and two NO3- anions. In the complex, [Co(C20H14N4S)(H2O)2]2+ cation, the tetra-dentate 6,6'-sulfanediylbis(2,2'-bi-pyridine) ligand coordinates to the CoII cation in the equatorial positions, while two water mol-ecules occupy the axial positions, forming a compressed octa-hedral CoN4O2 coordination sphere. The NO3- anions are linked to the [Co(C20H14N4S)(H2O)2]2+ cations via O-H⋯O hydrogen bonds, yielding a layered arrangement parallel to (001).

Field-Induced Slow Magnetic Relaxation in an Octacoordinated Fe(II) Complex with Pseudo-D2d Symmetry: Magnetic, HF-EPR, and Theoretical Investigations.

An octacoordinated Fe(II) complex, [FeII(dpphen)2](BF4)2·1.3H2O (1; dpphen = 2,9-bis(pyrazol-1-yl)-1,10-phenanthroline), with a pseudo-D2d-symmetric metal center has been synthesized. Magnetic, high-frequency/-field electron paramagnetic resonance (HF-EPR), and theoretical investigations reveal that 1 is characterized by uniaxial magnetic anisotropy with a negative axial zero-field splitting (ZFS) (D ≈ -6.0 cm-1) and a very small rhombic ZFS (E ≈ 0.04 cm-1). Under applied dc magnetic fields, complex 1 exhibits slow magnetic relaxation at low temperature. Fitting the relaxation time with the Arrhenius mode combining Orbach and tunneling terms affords a good fit to all the data and yields an effective energy barrier (17.0 cm-1) close to the energy gap between the ground state and the first excited state. The origin of the strong uniaxial magnetic anisotropy for 1 has been clearly understood from theoretical calculations. Our study suggests that high-coordinated compounds featuring a D2d-symmetric metal center are promising candidates for mononuclear single-molecule magnets.

Advances in site-specific integration of transgene in animal genome.

The traditional transgenic technologies, such as embryo microinjection, transposon-mediated integration, or lentiviral transfection, usually result in random insertions of the foreign DNA into the host genome, which could have various disadvantages in the establishment of transgenic animals. Therefore, a strategy for site-specific integration of a transgene is needed to generate genetically modified animals with accurate and identical genotypes. However, the efficiency for site-specific integration of transgene is very low, which is mainly caused by two issues. The first one is the low efficiency of inducing double-strand break (DSB) at the target site of host genome in the initial process. The second one is the low efficiency of homologous recombination repair (HDR) between the target site and the donor plasmid carrying homologous arm and foreign genes. HDR is the most common mechanism for site-specific integration of a transgene. DSBs can stimulate DNA repair mainly by two competitive mechanisms, HDR and nonhomologous end joining (NHEJ). Hence, activation of HDR or inhibition of NHEJ can promote the HDR in the integration processes, thereby optimizing a specific targeting of the transgene. In this review, we summarize the recent advances in strategies for improving the site-specific integration of foreign transgene in transgenic technologies.